As much as I'd like to think I know about intakes... I really don't know that much, but here are my two cents.

ITG filters flow alot more air... and are very common on racecars. K&N is more common in areas where less that perfect environments are available.

Here is where I really start talking about stuff I don't know...

ITG is supposed to flow more, but due to the more open area, it allows larger particles to the engine... bad. The K&N uses their OIL to create a static charge (I heard it somewhere) that helps reduce the flow of particles into the engine... good. Plus it's easier to re-oil the K&N over the ITG. I haven't seen a ITG recharger kit yet.

Now back to what I really know...

When I get my intake, I'll be running a K&N.